Refrigerants today include blends of e.g. hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs). HFOs have low global warming potential however are also less stable, risking compositional variations, with not much known yet. To add new knowledge, R452B (with R32, R125 and R1234yf) is analysed here, in used (7790 h in a heat pump) and pristine conditions, in a gas chromatograph with a thermal conductivity detector (TCD) and a flame ionization detector (FID). R452B was compared with moisture, N2 and a calibration blend containing CO2, R32, R125, R134a and R1234yf. The results yielded, besides the intended three components in R452B, also traces of R134a, moisture, possibly CO2 and several unknown compounds eluting before (thus lighter than) CO2. Some unknowns appeared only in TCD are thus non-combustible (including possibly O-2), while some appeared in both TCD and FID. The identification of these unknowns, calibrations for those and a comprehensive compositional analysis will follow.